Fuel injection pump for internal combustion engines of the diesel type



Sept. 12, 1933. H, D, 1,926,743

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES OF THE DIESEL TYPEFiled Sept. 30, 1929 ATTO RN EYS Patented Sept. 12, 1933 UNITED STATESPATENT OFFICE TYPE Harry D.. Hill, Lansing, Mich., assignor to HillDiesel Engine Company, Lansing, Mich., a corporation of MichiganApplication september so, 1929 Serial No. 396,340

l Claim.

The invention relates to fuel pumps for internal combustion engines. andmore particularly for use with engines of the Diesel type. It is usualto inject the fuel into a combustion chamber through a sprayer nozzleand to produce the required pressure for such injection by the opera-vtion of a plunger pump. As this `pump is frequently located at a pointremoved from the point of injection it is necessary to provide aconnecting conduit between the pump and the nozzle in which the fluid isconveyed und'er high pressure. There is also usually a valve at thedischarge end of the conduit which closes after each injection andremains closed during the portion of the cycle intermediate successiveinjections.

The quantity of fuel injected in successive operations of the pump iscontrolled by the operation of a governor, while the timing of theinjection is determined by the injection stroke of the plunger. Thereis, however, a certain lag in the timing of the injection due to theresiliency of the fluid and the conduit through which it passes whichstores 'a certain amount of energy and continues movement of the uidafter the plunger4 has reached the end of its injection stroke.

It is the object of the present invention to obtain a more positive andaccurately timed injection of the fuel and closingof the nozzle valve.This I have accomplished by the provisionof means operating at the endof the injection stroke of the plunger for instantaneously relieving thehigh pressure on the uid. The construction is such that after thisrelease of pressure the fuel kinjection conduit is again sealed andremains in i this condition until the succeeding period of fuelinjection. The invention-thereforev consists in the novel constructionas hereinafter described and shown in the drawing in which Figure 1 is alongitudinal section through my improved fuel injection pump;

Figures 2 and 3 show the plunger respectively at the beginning and atthe end of the injection stroke;

As shown, A is the cam shaft Whichoperates and times the fuel injection,B is a suitable casing in which .is located the' pump barrel C and D isthe plunger operating in this barrel.v The plunger is actuated by a camfollower E which is slidably secured in the casing B and which as shownis cup-shaped to embrace the plunger. F

is la spring for actuating the plunger in its return stroke, one end ofsaid spring bearing against a collar G on the plunger D and the otherend engaging an abutment on the casing.

The fuel inlet to the barrel C is through a lateral port H which isuncovered b'y the plunger as it approaches the end of its return stroke.The port H connects with a chamber I supplied with fuel under lowpressure by any suitable means (not shown). The quantity of fuel passingthrough the port H is, however, regulated by the adjustment of ametering pin J on a shank K slidable in a bearing L, the taperingportion of said pin engaging the mouth or entrance tube M leading to theport H. The position of the metering pin is regulated by a rock arm N ona shaft O which is rocked into different positions by the operations ofa governor (not shown). Thus the quantity of' fuel which is permitted.to pass into the barrel C during the brief interval in which the port His uncovered is determined by the restriction of the tube M by themetering pin J.

The discharge of the liquid from the pump barrel is through a portcontrolled by the check valve P closed by the spring P and after passingtheseV valves the fluid is conveyed-through a conduit Q to the sprayernozzle R.. This is preferably a finely apertured disk through whichfluid is forced and adjacent to this disk is the check valve S yieldablyforced to its seat by the spring S so that after each injection thesevalves P and S are intended to automatically close.

As has been stated, the liquid fuel when forced through the conduit Qunder high pressure due to the plunger D will store a certain amount ofenergy either by compression of the fluid or expansion of the conduit,and this will continue the discharge through the nozzle after theplunger has reached the end of its injection stroke. Inasmuch as themechanism is designed to time the injection by the cam and plungeroperated thereby, it is obvious that this lag in the discharge of theuid will interfere with the accuracy of the result. To avoid thisdefect, I have provided means for instantaneously releasing the pressureat the end of the' injection stroke of the plunger which is preferablyconstructed as follows:

'I'he plunger D is provided with a port which comes into registrationwith a relief port near the end of the injection stroke. As shown, theplunger has an annular vgroove T located to register with the port Hnear the end of the injection stroke and this annular groovecommunicated through a lateral bore T' with an axial bore T2 extendingto the end of the plunger. Thus as soon as the plunger moves to aposition where the groove T and port H register, the highpressure on theuid in the conduit Q is instantaneously released, dropping to thepressure within the chamber I. As this pressure is relatively low andmuch less than the pressure in the combustion chamber, the dischargethrough the nozzle will stop and the valves will be permitted to close.

The operation of the fuel pump occurs during the limited portion of theengine cycle and during the remainder of said cycle said pump remainsinactive. To avoid holding the relief port open during all of thisinactive portion of the cycle, the cam A is so constructed thatimmediately after the completion of its ejection stroke it will permitof the slight retraction of the plunger sufficient to close the reliefpassage. Thus as shown the portion A of the cam which reciprocates theplunger has a peak A2 corresponding to the limit of the ejection strokeand immediately adjacent to this peak is a cut-away portion A3 whichpermits suiiicient retraction of the plunger to close the relief port.There is then a concentric portion A4 of the cam which extends to thepoint where the portion A begins. Therefore, with this construction therelief of pressure is only an instantaneouscifect and is immediatelyfollowed by a closure ofthe relief ports which continue closed duringthe remainder of the cycle. -As has been stated, the amount of fuelwhich is admitted to the barrel is determined by the position of thetapering metering pin J during the interval in which the passage H isopen to the barrel. The stroke of the plunger D is constant but due tothe fact that the quantity of fuel admitted varies and also because ofthe resistance of the spring closed valves S and P the timing of initialinjection 'will be varied. This is a desirable feature for when theengine is operating under full load it is advantageous to advance thetime of ignition as is automatically accomplished by my construction.

What I claim as my invention is:

A fuel injection pump for internal combustion engines comprising areciprocable plunger, a barrel in which said plunger reciprocatesprovided with a lateral inlet passage uncovered by said plunger when inits retracted position, a conduit leading from said barrel to theinjection nozzle, a relief passage having co-operating portions in saidplunger and said barrel adapted to register at the completion of theejection stroke, and means for operating said plunger during a. portionof the engine cycle in the sequence of first retracting and thenadvancing the plunger to the completion of its ejection stroke immedi.

ately followed by a slight retraction sufficient to quickly close therelief port and for holding the plunger stationary in this positionduring the remainder of the cycle.'

HARRY D. HILL.

